Attribution Of Extreme Weather Events Research Articles

A forecast-model-based extreme weather event attribution system developed for Aotearoa New Zealand

A largely automated extreme weather event (EWE) attribution system has been developed that uses the Weather Research and Forecast numerical weather prediction model to simulate EWEs under current and pre-industrial climate conditions. The system has been applied to two extreme precipitation events in Aotearoa New Zealand with the goal of quantifying the effect of anthropogenic climate change on the severity of these events. The forecast simulation of the target event under current climate conditions constitutes the first scenario (ALL). We then apply a climate change signal in the form of delta fields in sea-surface temperature, atmospheric temperature and specific humidity, creating a second ‘naturalised’ scenario (NAT) which is designed to represent the weather system in the absence of human interference with the climate system. A third scenario, designed to test for coherence, is generated by applying deltas of opposite sign compared to the naturalised scenario (ALL+). Each scenario comprises a 22-member ensemble which includes one simulation that was not subject to stochastic perturbation. Comparison of the three ensembles shows that: (1) the NAT ensemble develops an extreme event which resembles the observed event, (2) the severity, i.e. maximum intensity and/or the size of area affected by heavy precipitation, changes when naturalising the boundary conditions, (3) the change in severity is consistently represented within the three scenarios and the signal is robust across the different ensemble members, i.e. it is typically shown in most of the 22 ensemble members. Thus, the attribution system presented here can be used to provide information about the influence of anthropogenic climate change on the severity of specific extreme events.

Attribution of Extreme Events to Climate Change

Within the past decade, the attribution of extreme weather events and their impacts has enabled scientists, the public, and policymakers alike to connect real-world experiences of extreme weather events with scientific understanding of anthropogenic climate change. Attribution studies of recent extreme weather events have formed a new and important line of evidence in the most recent Intergovernmental Panel on Climate Change (IPCC) assessment report understanding present-day impacts of climate change. IPCC studies using different methods of event attribution have been assessed together, highlighting that these differences are smaller than the academic discourse on the methods suggests. This development raised two important research questions the science needs to answer: First, how do we formally combine attribution statements using highly conditional methods with probabilistic assessments of how climate change alters the likelihood and intensity of extreme weather events? Second, under what circumstances are individual attribution studies still necessary and to what extent do existing attribution studies provide enough information to answer societal questions? Furthermore, the scientific development still leaves important gaps, particularly in countries of the Global South, leading to ethical questions around the need and requirement of attribution of extreme events in policy contexts, informing adaptation and loss and damage and the role of vulnerability.

Toward Near-Real-Time Attribution of Extreme Weather Events in Aotearoa New Zealand

© 2022 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).CORRESPONDING AUTHOR: Jordis S. Tradowsky, jordis@bodekerscientific.com

Operational extreme weather event attribution can quantify climate change loss and damages

“It is now well established that the influence of anthropogenic climate change on certain individual extreme weather events can be quantified by event attribution techniques. It is time that these activities move from the research community to the operational centers. Such routine evaluation of the human influence on extreme weather increases our scientific understanding and informs the public of climate change impacts. Furthermore, quantification of the human influence on extreme weather can be used to fairly evaluate climate change induced loss and damages”.

Attribution of extreme weather events: how does climate change affect weather?

Attribution of extreme weather events: how does climate change affect weather?

Attribution matters: Revisiting the link between extreme weather experience and climate change mitigation responses

Abstract The literature suggests that extreme weather experiences have potential to increase climate change engagement by influencing the way people perceive the proximity and implications of climate change. Yet, limited attention has been directed at investigating how individual differences in the subjective interpretation of extreme weather events as indications of climate change moderate the link between extreme weather experiences and climate change attitudes. This article contends that subjective attribution of extreme weather events to climate change is a necessary condition for extreme weather experiences to be translated into climate change mitigation responses, and that subjective attribution of extreme weather to climate change is influenced by the psychological and social contexts in which individuals appraise their experiences with extreme weather. Using survey data gathered in the aftermath of severe flooding across the UK in winter 2013/2014, personal experience of this flooding event is shown to only directly predict perceived threat from climate change, and indirectly predict climate change mitigation responses, among individuals who subjectively attributed the floods to climate change. Additionally, subjective attribution of the floods to climate change is significantly predicted by pre-existing climate change belief, political affiliation and perceived normative cues. Attempts to harness extreme weather experiences as a route to engaging the public must be attentive to the heterogeneity of opinion on the attributability of extreme weather events to climate change.

Extreme weather event attribution science and climate change litigation: an essential step in the causal chain?

The 2017 North Atlantic hurricane season caused the highest disaster-related losses ever seen in the United States, with many people asking questions about the causes and liabilities for the impacts of these kinds of events. As climate-related loss and damage mount, there is growing interest in the role of law in dealing with the complex and multi-scalar problem of climate change. This article builds on a shorter piece entitled ‘Acts of God, human influence and litigation’ published by the authors in Nature Geoscience in August 2017. It is an interdisciplinary and cross-jurisdictional analysis of the emerging science of extreme weather event attribution (which analyses the human impact on extreme weather events), and the implications this new science may have for the law, litigation and the scope of the duty of care of a range of actors. We suggest that the science of event attribution may become a driver of litigation, as it shifts understanding of what weather is expected and, relevantly for law, foreseeable. This may have an impact on the duties of government actors as well as private parties. We explain the discipline of event attribution science to lawyers, discuss some technical issues related to the use of this evidence in court and make some suggestions regarding the types of ‘climate change’ cases it may influence. We conclude that the first kind of litigation to emerge is most likely to arise from failures to adapt to, or to prepare for, our changing climate.

Probabilities of Causation of Climate Changes

Multiple changes in Earth’s climate system have been observed over the past decades. Determining how likely each of these changes is to have been caused by human influence is important for decision making with regard to mitigation and adaptation policy. Here we describe an approach for deriving the probability that anthropogenic forcings have caused a given observed change. The proposed approach is anchored into causal counterfactual theory ( Pearl 2009 ), which was introduced recently, and in fact partly used already, in the context of extreme weather event attribution (EA). We argue that these concepts are also relevant to, and can be straightforwardly extended to, the context of detection and attribution of long-term trends associated with climate change (D&A). For this purpose, and in agreement with the principle of fingerprinting applied in the conventional D&A framework, a trajectory of change is converted into an event occurrence defined by maximizing the causal evidence associated to the forcing under scrutiny. Other key assumptions used in the conventional D&A framework, in particular those related to numerical model error, can also be adapted conveniently to this approach. Our proposal thus allows us to bridge the conventional framework with the standard causal theory, in an attempt to improve the quantification of causal probabilities. An illustration suggests that our approach is prone to yield a significantly higher estimate of the probability that anthropogenic forcings have caused the observed temperature change, thus supporting more assertive causal claims.

Regional decision-makers as potential users of Extreme Weather Event Attribution - Case studies from the German Baltic Sea coast and the Greater Paris area

Extreme Event Attribution has raised increasing attention in climate science in the last years. It means to judge the extent to which certain weather-related extreme events have changed due to human influences on climate with probabilistic statements. Extreme Event Attribution is often anticipated to spur more than just scientific ambition. It is able to provide answers to a commonly asked questions after extreme events, namely, ‘can we blame it on climate change’ and is assumed to support decision-making of various actors engaged in climate change mitigation and adaptation. More in-depth research is widely lacking about who these actors are; in which context they can make use of it; and what requirements they have, to be able to actually apply Extreme Event Attribution. We have therefore addressed these questions with two empirical case studies looking at regional decision-makers who deal with storm surge risks in the German Baltic Sea region and heat waves in the Greater Paris area. Stakeholder interviews and workshops reveal that fields of application and requirements are diverse, difficult to explicitly identify, and often clearly associated with stakeholders' specific mandate, the hazard background, and the regional socio-economic setting. Among the considered stakeholders in the Baltic Sea region, Extreme Event Attribution is perceived to be most useful to awareness-raising, in particular for climate change mitigation. They emphasised the importance of receiving understandable information - and that, rather later, but with smaller uncertainties than faster, but with higher uncertainties. In the Paris case, we typically talked to people engaged in adaptation with expertise in terms of climate science, but narrowly defined mandates which is typical for the Paris-centred political system with highly specialised public experts. The interviewees claimed that Extreme Event Attribution is most useful to political leverage and public discourses. If novel information like this is not sorted out a priori, it needs to be clearly linked to impacts, preferably as monetary values lost. These examples underline the significance of conducting case-specific stakeholder mappings and consultation. Overall, our studies can thereby provide methods and exemplary empirical evidence to support developing useful services from Extreme Event Attribution for targeted groups of users.

An Independent Assessment of Anthropogenic Attribution Statements for Recent Extreme Temperature and Rainfall Events

The annual “State of the Climate” report, published in the Bulletin of the American Meteorological Society (BAMS), has included a supplement since 2011 composed of brief analyses of the human influence on recent major extreme weather events. There are now several dozen extreme weather events examined in these supplements, but these studies have all differed in their data sources as well as their approaches to defining the events, analyzing the events, and the consideration of the role of anthropogenic emissions. This study reexamines most of these events using a single analytical approach and a single set of climate model and observational data sources. In response to recent studies recommending the importance of using multiple methods for extreme weather event attribution, results are compared from these analyses to those reported in the BAMS supplements collectively, with the aim of characterizing the degree to which the lack of a common methodological framework may or may not influence overall conclusions. Results are broadly similar to those reported earlier for extreme temperature events but disagree for a number of extreme precipitation events. Based on this, it is advised that the lack of comprehensive uncertainty analysis in recent extreme weather attribution studies is important and should be considered when interpreting results, but as yet it has not introduced a systematic bias across these studies.

Real-time extreme weather event attribution with forecast seasonal SSTs

Within the last decade, extreme weather event attribution has emerged as a new field of science and garnered increasing attention from the wider scientific community and the public. Numerous methods have been put forward to determine the contribution of anthropogenic climate change to individual extreme weather events. So far nearly all such analyses were done months after an event has happened. Here we present a new method which can assess the fraction of attributable risk of a severe weather event due to an external driver in real-time. The method builds on a large ensemble of atmosphere-only general circulation model simulations forced by seasonal forecast sea surface temperatures (SSTs). Taking the England 2013/14 winter floods as an example, we demonstrate that the change in risk for heavy rainfall during the England floods due to anthropogenic climate change, is of similar magnitude using either observed or seasonal forecast SSTs. Testing the dynamic response of the model to the anomalous ocean state for January 2014, we find that observed SSTs are required to establish a discernible link between a particular SST pattern and an atmospheric response such as a shift in the jetstream in the model. For extreme events occurring under strongly anomalous SST patterns associated with known low-frequency climate modes, however, forecast SSTs can provide sufficient guidance to determine the dynamic contribution to the event.

Stakeholder Perspectives on the Attribution of Extreme Weather Events: An Explorative Enquiry

Abstract Recent extreme weather events and their impacts on societies have highlighted the need for timely adaptation to the changing odds of their occurrence. Such measures require appropriate information about likely changes in event frequency and magnitude on relevant spatiotemporal scales. However, to support robust climate information for decision-making, an effective communication between scientists and stakeholders is crucial. In this context, weather event attribution studies are increasingly raising attention beyond academic circles, although the understanding of how to take it beyond academia is still evolving. This paper presents the results of a study that involved in-depth interviews with stakeholders from a range of sectors about potential applications and the general usefulness of event attribution studies. A case study of the hot and dry summer 2012 in southeast Europe is used as a concrete example, with a focus on the applicability of attribution results across sectors. An analysis of the interviews reveals an abundant interest among the interviewed stakeholders and highlights the need for information on the causes and odds of extreme events, in particular on regional scales. From this data key aspects of stakeholder engagement are emerging, which could productively feed back into how probabilistic event attribution studies are designed and communicated to ensure practical relevance and usefulness for the stakeholder community.

Attribution of extreme weather events in Africa: a preliminary exploration of the science and policy implications

Extreme weather events are a significant cause of loss of life and livelihoods, particularly in vulnerable countries and communities in Africa. Such events or their probability of occurring may be, or are, changing due to climate change with consequent changes in the associated risks. To adapt to, or to address loss and damage from, this changing risk we need to understand the effects of climate change on extreme weather events and their impacts. The emerging science of probabilistic event attribution can provide scientific evidence about the contribution of anthropogenic climate change to changes in risk of extreme events. This research has the potential to be useful for climate change adaptation, but there is a need to explore its application in vulnerable developing countries, particularly those in Africa, since the majority of existing event attribution studies have focused on mid-latitude events. Here we explain the methods of, and implications of, different approaches to attributing extreme weather events in an African context. The analysis demonstrates that different ways of framing attribution questions can lead to very different assessments of change in risk. Crucially, defining the most appropriate attribution question to ask is not a science decision but one that needs to be made in dialogue with those stakeholders who will use the answers. This is true of all attribution studies but may be particularly relevant in a tropical context, suggesting that collaboration between scientists and policy-makers is a priority for Africa.

Attributing weather extremes to ‘climate change’

Over the last 30 years, scientific research has increasingly implicated human activities in contemporary regional- to global-scale climatic change. Over the last decade, this research has extended to the detection of the fingerprint of human activities on individual extreme weather events. Is it possible to say that this or that weather extreme was ‘caused by’ human activities? Pursuing answers to this question raises many difficult philosophical, epistemological and political issues. In this progress report, I survey the nascent science of extreme weather event attribution by examining the field in four stages: motivations for extreme weather attribution, methods of attribution, some example case studies and the politics of weather event attribution. There remain outstanding political dangers and obstacles for extreme weather attribution if it is to be used, as some claim it can and should be, for guiding climate adaptation investments, for servicing the putative loss and damage agenda of the UN Framework Convention on Climate Change or for underpinning legal claims for liability for damages caused by extreme weather.

Loss and damage attribution

If research on attribution of extreme weather events is to inform emerging climate change policies, it needs to diagnose all of the components of risk.